The invention relates to novel fluoromethyl ketones of the formula I ##STR2## in which is H, an alkyl or alkenyl radical having 1 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF.sub.3 or at least monosubstituted by halogen, it also being possible for one or more CH.sub.2 groups in these radicals to be replaced, in each case independently of one another by --O--, --S--, ##STR3## --CO--, --CO--O--, --O--CO-- or --O--CO--O--, in such a way that O atoms are not linked directly to one another,
A.sup.1 and A.sup.2 are each, independently of one another, a PA1 Z.sup.1 and Z.sup.2 are each, independently of one another, --CO--O--, --O--CO--, --CH.sub.2 O--, --OCH.sub.2 --, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C-- or a single bond, and one of the radicals Z.sup.1 and Z.sup.2 is alternatively --(CH.sub.2).sub.4 -- or --CH.dbd.CH--CH.sub.2 CH.sub.2 --, PA1 is H, F or Cl and PA1 is 0, 1 or 2. PA1 In addition to one or more compounds of the formula I, the medium contains further compounds, preferably selected from the following group: ##STR25## in which the individual radicals are defined as follows: R': alkyl, oxaalkyl, fluoroalkyl or alkenyl, in each case having up to 7 carbon atoms, PA1 X': F, Cl, CF.sub.3, OCF.sub.3 or OCHF.sub.2, PA1 Y' and Z: each, independently of the other, H or F, and PA1 r: 0 or 1.
(a) trans-1,4-cyclohexylene radical in which, in addition, one or more non-adjacent CH.sub.2 groups may be replaced by --O-- and/or --S--, PA2 (b) 1,4-phenylene radical in which, in addition, one or two CH groups may be replaced by N, or PA2 (c) radical from the group consisting of 1,4-cyclohexenylene, 1,4-bicyclo(2,2,2)-octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl and 1,2,3,4-tetrahydronaphthalene-2,6-diyl,
it being possible for the radicals (a) and (b) to be substituted by one or two fluorine atoms.
The invention furthermore relates to the use of these compounds as components of liquid-crystalline media, and to liquid-crystal and electro-optical display elements containing the liquid-crystalline media according to the invention.
The compounds of the formula I can be used as components of liquid-crystalline media, in particular for displays based on the principle of the twisted cell, the guest-host effect, the effect of deformation of aligned phases or the effect of dynamic scattering.